Roof and waterproofing membranes and linings have long been used to protect buildings, to contain water in ponds and decorative water features, to prevent leaching of contaminants from landfills, and for other purposes. While these membranes have utility, leakage through the membranes is an ongoing problem. The efforts to contain and locate leakage have resulted in the rise of specialized consultants, air and vacuum testable membranes, and, in recent history, electrical testing methods that not only determine if a leak is present in a membrane system, but where the leak is located.
Leakage in existing roofs is a particular problem, especially when the roof has a nonconductive element at the bottom of the roofing envelope next to the deck, such as a vapor barrier or a secondary roofing membrane. In these cases, water leaking into the roofing envelope can saturate the insulation and other elements in the envelope without actually leaking into the building because the lowermost membrane acts as a barrier to the water. In time, water might run into the building via penetrations, such as vent stacks, curbs for mechanical equipment, conduits etc., through the roofing envelope and be visible from underneath. By this time, corrective action may encompass cutting cores in the roofing envelope to determine the extent of water damage; removing a large portion of the roof; performing infrared or other tests to indicate the current status of the roofing envelope; etc.
Additionally, when the roofing envelope becomes saturated with water, a portion of the planned energy efficiency from the roofing envelope is lost. The building structure may also experience the corrosive effects of water, therefore compromising its penetrations. Unbeknownst to anyone, this process is occurring in thousands of roofs across North America and, indeed, in the built environment anywhere in the world.
There are methods that have been developed to address the above described problems including manual methods, such as capacitance testing, infrared scanning, and moisture probing. In addition, there are automatic systems driven by computers with sensors built into or retrofitted into the non-conductive insulation and other non-conductive materials which comprise the roofing envelope.
One known method of placing such an automatic system into a non-conductive envelope is to install relative humidity sensors in the roofing envelope, where the sensors measure humidity and temperature. An array of such sensors can give a representation of moisture conditions in a roofing envelope. Such a system is provided by Progeo GmbH of Germany and other vendors, and these systems have been used on projects in the United States. Such systems are limited in that the sensors require a certain amount of free air around them in order to determine the ambient moisture content of any part of the roofing envelope, and each sensor is only one point, measuring the relative humidity of a very small area around its location. Further, there is no guarantee that any air will circulate in the roofing envelope, and if the free flow of air is cut off, especially given the impermeable nature of closed-cell insulations in today's roofing envelopes, the sensors will not be able to sense variations in moisture, but only temperature changes.
The computer attached to such a system is given the task of correlating all the data received from the sensors in these distinct, small areas, and of producing a table, graph, or other graphic based on the extrapolations of these data. In order for the data to be at all relevant, the computer must make a correlation reading from a sensor located on the outside of the roofing envelope so that it can compare trends in relative humidity on the outside of the roof to the trends being determined by data from the sensors within the roofing envelope. The results are skewed when the temperature changes within the roofing envelope, outside the roofing envelope, or both. The skew is particularly pronounced when temperature changes precipitously, and a certain amount of time is required, sometimes days or weeks, before the system can stabilize enough to produce relevant data again. Even so, relevant data can only be surmised, as the circulation of free air in the roofing envelope cannot be adequately determined, especially across the entire expanse of the envelope. If these systems are retrofitted using tubes inserted into holes cut into the roofing envelope, the temperature sensed in the tubes is different from the actual temperature in the roofing envelope as a whole, and incorrect temperature and the contingent relative humidity measurements are inaccurate, causing false leakage alerts. Further, in order to make such a system more responsive or accurate, sensors must be deployed much closer to one another so the computer will have a greater number of points from which to draw and extrapolate data, driving the cost of the system up. In summary, such systems have significant drawbacks. In addition, the Inventor has developed several automatic systems, such as those disclosed in U.S. Pat. Nos. 8,566,051, 9,341,540, and 9,500,555 and U.S. patent application Ser. No. 14/061,480, each of which is hereby incorporated by reference.
Another known automatic system requires a grid of hydrophobic cables, the cross-over points of which, when wetted from water flowing through the roofing membrane, make a closed circuit that identifies which portion of the grid is wet and allows location of the leakage through the membrane. This system requires water to make its way to the cross-over points to trigger an alarm and a significant flooding of a portion of the roofing envelope might occur before an alarm is tripped. Such a system is sold under the trademark DETEC.